There is conventionally known an antenna device adaptive to two frequencies. An antenna device installed on a roof or the like of a vehicle is preferably installed at the highest position of the vehicle in terms of receiving sensitivity, while there is desired a low-profile antenna device in order to meet a height regulation and the like. Recently, a “lower-profile” antenna device, such as so-called a shark-fin type antenna device, in which the low-profile characteristic is further strengthened, is being developed.
As such a low-profile antenna device, there is known an antenna device provided with so-called a top load portion so as to perform satisfactory operation at the two frequencies. For example, Patent Document 1 discloses a technology in which an umbrella-shaped top load portion is provided at a leading end of an element portion installed upright from a base portion. This can reduce a length of the element portion to thereby realize a “lower-profile” antenna device.